Transparent thermoplastic resin pellet manufacturing method

Abstract

A method for producing a transparent thermoplastic resin pellet comprising a step of kneading a transparent thermoplastic resin with a kneader under a condition under which a damage history calculated according to the following formula is 500 to 2,500:Damage history={Residence time (tr)}×{Shear rate (γ)}Residence time (tr)=(W×H×L) / Q Shear rate (γ)=(π×D×N) / H in the formulae, W represents a screw groove width (pitch) [cm]; H represents a screw groove depth [cm]; L represents a screw length [cm]; Q represents a resin supply amount [g / s]; D represents a screw diameter [cm]; and N represents a screw rotation number [rps].

Description

TECHNICAL FIELD[0001]The present invention relates to a method for manufacturing a transparent thermoplastic resin pellet, and in particular, the present invention relates to a method for manufacturing a pellet of a transparent thermoplastic resin such as a polycarbonate resin, etc.BACKGROUND ART[0002]In recent years, transparent thermoplastic resins such as polyarylate resins, polymethyl methacrylate resins, polystyrene resins and polycarbonate resins are preferably used as a molding material in the optical field. In these applications, the size or amount of foreign matter (e.g., dusts, carbides, gelled products, etc.) in the resin, and whether the hue of the resin is good or bad largely influences the quality of the product. In particular, in the manufacture of an optical light guide plate, a change of hue of the resin constituting a substrate and a foreign matter in a substrate give an extremely large influence against the reliability of the product.[0003]In a method of obtaining...

AI Technical Summary

Benefits of technology

The present invention provides a method to produce a transparent thermoplastic resin pellet that contains a low amount of gels and is less yellow when molded into a sheet or film. This results in a more desirable product with improved quality.

Problems solved by technology

In particular, in the manufacture of an optical light guide plate, a change of hue of the resin constituting a substrate and a foreign matter in a substrate give an extremely large influence against the reliability of the product.

In a method of obtaining a molded substrate of a relatively small and medium sized mobile phone or the like by means of injection molding, or a method of manufacturing a sheet molded substrate or film molded substrate by melt extruding a transparent thermoplastic resin and extrusion molding the extruded molten material, it is considered that it is very difficult to reduce gels resulting from the resin.

In particular, in the case where it is intended to manufacture a sheet molded substrate or film molded substrate by using a thermoplastic resin which is liable to generate a gel, a manufacture condition becomes severe for the purpose of decreasing the amount of gels generated in the sheet molded substrate or film molded substrate.

However, when a screw made of a combination of elements is used, large sized colored materials and foreign matter such as gelled products are often generated.

However, according to this technique, if a material having low corrosion resistance is used for the screw, there is a concern that crevice corrosion of the screw is generated due to a stress to generate contamination with foreign matter, resulting in a hindrance to reduction of foreign matter.

In addition, a screw noise is generated due to torque variations or screw vibration at the time of resin extrusion depending on the constitution, resulting in not only a hindrance to stable production but metal fatigue or deterioration of the screw.

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